But the concepts of health and disease are just briefly reviewed and Martin and co-authors refer that productivity is commonly used as a surrogate definition of health in veterinary medi
Trang 1Open Access
Review
The conceptualisation of health and disease in veterinary medicine
Stefan Gunnarsson*
Address: Section of Animal Hygiene, Department of Animal Environment and Health, Swedish University of Agricultural Sciences (SLU), P.O Box
234, S-532 23 Skara, Sweden
Email: Stefan Gunnarsson* - stefan.gunnarsson@hmh.slu.se
* Corresponding author
Abstract
Background: The concept of health, as well as the concept of disease, is central in veterinary
medicine However, the definitions "health" and "disease" are not generally acknowledged by
veterinarians The aim of this study was to examine how the concepts "health" and "disease" are
defined in veterinary textbooks
Methods: Veterinary textbooks in several disciplines were investigated, but only textbooks with
explicit definitions of the concepts were selected for examination
Results: Eighty out of the 500 relevant books within veterinary medicine were written for
non-veterinarians Eight percent of the books had an explicit definition of health and/or disease More
frequently, textbooks written for non veterinarians did have definitions of health or disease,
compared to textbooks written for professionals A division of health definitions in five different
categories was suggested, namely:
1 Health as normality, 2 Health as biological function, 3 Health as homeostasis, 4 Health as
physical and psychological well-being and 5 Health as productivity including reproduction
Conclusion: Few veterinary textbooks had any health or disease definition at all Furthermore,
explicit definitions of health stated by the authors seemed to have little impact on how health and
disease are handled within the profession Veterinary medicine would probably gain from
theoretical discussions about health and disease
Background
The concept of health, as well as the concept of disease,
must be regarded as essential to veterinary medicine
Nev-ertheless, it appears to be uncommon that broader
discus-sions about these basic concepts occur within the
veterinary society The increasing diagnostic possibilities
to identify diseases make it crucial to define disease and
health, as this basic distinction gives the very fundament
of disease classification
The naive definition of health in veterinary medicine seems to be that health is no more than the very absence
of disease, which can be considered as a dichotomous def-inition This position is often the case for basic assump-tions in e.g epidemiology, where the disease frequency commonly is calculated based on that disease is binary, which means that either the animal has the disease or it does not have the disease
Published: 07 November 2006
Acta Veterinaria Scandinavica 2006, 48:20 doi:10.1186/1751-0147-48-20
Received: 30 September 2006 Accepted: 07 November 2006 This article is available from: http://www.actavetscand.com/content/48/1/20
© 2006 Gunnarsson; licensee BioMed Central Ltd
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Trang 2The epidemiological methods used to investigate the
excellence of a disease test, e.g the sensitivity and the
spe-cificity of a serological method, is built on the understated
assumptions of well-defined concepts of disease and
health However, it seems to be rare that any evaluation of
diagnostic methods is based on any scrutiny or more
pre-cise definitions For example in a well known textbook in
veterinary epidemiology quite extended parts of the book
emphasize the theoretical problems associated with
diag-nostic tests [1] But the concepts of health and disease are
just briefly reviewed and Martin and co-authors refer that
productivity is commonly used as a surrogate definition
of health in veterinary medicine, although this has been
seriously questioned by several others [e.g [2]]
Pathology has always been an essential part of veterinary
medicine It is more or less self-evident that the
patholo-gist should be able to determine health from disease in
order to put an accurate diagnosis Nevertheless, it seems
rare to find any explicit definition of these central
con-cepts or even to find the subject being investigated further
No matter in what area the veterinarian is active, the daily
work involves, directly or indirectly, health and disease in
animals Therefore, it is logical to examine how different
concepts of disease are used within veterinary medicine,
and to examine textbooks in veterinary medicine, e.g
vet-erinary pathology, internal medicine and epidemiology
The aim of the present study is to examine how the
con-cepts of "health" and "disease" are defined in veterinary
textbooks in pathology, epidemiology, internal medicine
and other areas Definitions of health and disease found
in various textbooks of veterinary medicine are examined
and categorised Furthermore, the implications of the
dif-ferent health definitions are discussed
Methods
The veterinary textbooks at the libraries of the Swedish
University of Agricultural Sciences (SLU) were examined
during the spring of 2003 The literature investigated
com-piled veterinary textbooks in several disciplines, such as
pathology, internal medicine, bacteriology and
immunol-ogy
The approach of examining the literature was to perform
a scanning of the tables of content, indexes and
introduc-tory chapters of every volume The scanning was done to
identify any definition or theoretical discussion about
health or disease Only textbooks with explicit definitions
of health and disease were selected for further
examina-tion Thus, this study does not investigate implicit
defini-tions of health and disease, as the identification of such
definitions would demand far more advanced analyses, as
well as, there would be an increased risk of getting arbi-trary definitions
Results
About 80 out of the 500 relevant books I found within veterinary medicine were written for non-veterinarians, such as veterinary nurses, farmers or the common man Thirty-nine of the 500 books (8%) comprised any explicit form of, more or less developed, definition of health and/
or disease Twenty-two books out of these 39 were written for veterinarians or veterinary students, five were veteri-nary dictionaries, two were handbooks for veteriveteri-nary nurses and ten were written for farmers or animal owners Twenty-five volumes out of the 39 were written in English, four were in German, five were in Swedish, two were in Norwegian, two were in Danish and one volume were written in French
Four out of 39 volumes were available in several editions These different editions were counted as single hand-books, and special attention was paid to any added or extended health or disease definition Different editions revealed an extended or modified definition of health [3-7] Other handbooks had unchanged text sections about health/disease throughout several editions, e.g a German textbook for veterinary nurses [8-10]
A higher proportion of textbooks written for non-veteri-narians contained definitions of health or disease, com-pared to textbooks written for veterinarians (15% versus 7%) The three textbooks about alternative veterinary medicine with explicit health definition were all written for laymen and specifically covered homeopathic treat-ment of animals [11-13] These books were not only giv-ing a definition of health from the point of view of alternative veterinary medicine, but also a health defini-tion of what the authors saw as convendefini-tional medicine, which they rejected However, there were no references to other publications in these books
Most books had only one single definition of health or disease The exception was, apart from the books in alter-native medicine, a dictionary of veterinary medicine where alternative definitions of health were given [14,15]
Discussion
Few veterinary textbooks had any health definition at all
In general, common textbooks of pathology were lacking any suggestion of how to define health and disease Typi-cally, the textbooks of pathology and internal medicine comprised chapters about each system of organs, i.e one chapter about diseases of the integument, one about dis-ease of the respiratory system, one about disdis-ease of the digestive system and so on These textbooks contained contributions from several authors, responsible for text
Trang 3sections of the diseases of an organ system or a group of
diseases Then the book chapters were put together by the
editors [e.g [16,17]]
Categories of health definitions
A subdivision of health definitions is in itself arbitrary
However, such a division may increase the possibility to
comprehend heterogeneous items of more or less
devel-oped definitions of health and disease The subdivision
presented here should be regarded as a tool to bring order
in this study, rather than to establish a definition of
schools of the subject once and for all
Different approaches to the concept of health and disease
were found in the literature reviewed and they can be split
into the following five categories:
1 Health as normality
2 Health as biological function
3 Health as homeostasis
4 Health as physical and psychological well-being
5 Health as productivity including reproduction
1 Health as normality
It seems common to define health and disease in terms of
normality or abnormality However, definitions referring
to health as normality were usually very limited in their
extension and sometimes only fragments were found An
example of normality definition comes from a manual for
animal health auxiliary personnel written by the Food and
Agriculture Organization of the United Nations [18],
where a healthy animal is described to have a normal
appearance and behaviour The animal should have
nor-mal features, including nornor-mal body position and
move-ments This definition is actually not a definition of the
concept of health as such, but an operational definition of
clinical health, assuming normality
John Webster [19] has a similar approach to health in his
disease definition which relates disease to a normal state
and that "ill health always appear as departure from
nor-mality" Webster also puts our attention to the
impor-tance of getting clinical experience of the normal health
animal in order to understand the normal variation of
healthy animals
In a German veterinary dictionary 'disease' is defined as a
disturbance of the normal function of the body [20] A
similar definition is given by Arnall and Keymer [21], who
define health as a soundness of the body and an absence
of disease, which assume that there is a normality of
health However, the authors are referring to diverse defi-nitions of health without giving a clear opinion of their own
Baker and Greer [22] give a semantic analysis of the dis-ease concept before they propose a normality-based health concept They define disease "as 'not at ease' because the prefix 'dis' denotes reversal or separation from the root 'ease' Animal ill health is synonymous with the word 'disease'."
In the previous definitions there are clearly stated attempts to base the health concept on normality, but ele-ments of biological function can also be introduced as rel-evant to normality definition [22,23] Particularly Baker and Greer [22], in a passage about that "structural defect
or functional impairment of the animal body", implies that they do not only define health as normality, but that they also think that health is linked to a biological func-tioning
2 Health as biological function
Slauson and Cooper [24] propose in their textbook about comparative pathology that disease can be seen as a man-ifestation of malfunctioning physiology or physiology that has gone wrong They think that disease ultimately reflects structural or functional alteration in the cells of which all living things are made, which is the common idea within pathology
Gillespie and Timoney [25] give a similar definition of disease, namely that a disease is defined disturbances of proper performance of body functions, or as they put it:
"Disease may be defined as an alteration of the state of the body, or of some of its organs, which interrupts or dis-rupts the proper performance of the bodily functions Functional disturbance soon is manifested by physical signs which usually can be detected by others."
The pathologist Norman F Cheville [26] expresses that veterinary pathology is abnormal biology in a wide sense, and that "pathology is essentially the search for and the study of lesions, the abnormal structural and functional changes that occur in the body."
The idea of health as based on biological functioning is related to the idea of homeostasis, which could be said to develop the idea of functioning more precise by setting the boundaries of functioning
3 Health as homeostasis
Health defined as homeostasis is an old idea, but still it is
a common way of looking at health and disease The con-cept of homeostasis is related to the maintenance of a del-icate balance within the organism or within the processes
Trang 4in the organism Here is one example: "Disease arises
when the normal interplay of the body functions is
dis-turbed It is depending on the constitution of the
organ-ism, on the disposition for disease and on the disease
causes that influence the body, e.g infectious agents,
envi-ronmental factors, toxic substances and alteration of
nutrients" [[8-10], translated from German by the
author]
The idea of homeostasis seems so firmly established
within the discipline of physiology that it is not just
regarded as an approach to describe physiological
proc-esses; it is considered to be a law of nature in the same way
as the idea of evolution is viewed as a law of nature not a
biological theory
The idea of health as homeostasis is commonly used
within veterinary homeopathy In the three homeopathy
books found, the discussions about health were quite
extended and the homeostasis idea was contrasted to the
assumed ideas of conventional medicine The
homeosta-sis idea was expressed as being holistic, which can be
illus-trated by Christopher Day [12], who writes about
homeopathic veterinary medicine in comparison to
con-ventional medicine, as he looking at it
"In holistic terms, the word 'health' implies the concept of
a mind and body together in harmony with the
environ-ment When the organism, comprising the mind and the
body, is out of the harmony within itself or with its
envi-ronment, then we have the state of disease (literally
dis-ease)
Modern conventional medicine tends to view disease as a
set of signs and symptoms, recognisable combinations of
which are called 'disease' Each of these given a name and
is assumed to have an identity of its own In holistic
med-icine we view disease differently We see the signs or
symptoms simply as a result of, and expression of the
body's reaction to, the disease forces which impinge upon
it, threatening to disturb its internal equilibrium Like all
systems in equilibrium, the body – a very sensitive and
active equilibrium system-reacts to disturbing forces in an
attempt to retain or regain balance." [12]
Homeopathic health definitions are often stated to be
"holistic" and based on the idea that health is depending
on homeostasis However, as health definition found in
conventional veterinary textbooks also can be based on
the homeostasis idea, it can not be deduced that
homeo-static thinking logically leads to homeopathic medicine
One example of this is that Lagerlöf, Hallgren and Ekesbo
[27] define health as a state where all organs are in a
deli-cate balance within the organism and with the
surround-ing world This definition has been further refined by
Ekesbo [27,28] The authors Lagerlöf, Hallgren and Ekesbo clearly belong to classic veterinary medicine and not the homeopathic school
4 Health as physical and psychological well-being
It is common in the debate about animal welfare to pro-pose definitions of health that includes psychological aspects of health [2,29,30] However, it seems uncommon that welfare and well-being are included in the health def-initions in veterinary textbooks One exception is Martin and co-authors [1] that start off with giving references to the human health definition stated by the World Health organisation (WHO), i.e that health is "a state of com-plete physical, mental, and spiritual well being", but they also think that productivity is a substantial part of health
in farm animals
If health is defined as physical and psychological well-being, there are problems associated with applying the definition to all animals Domestic animals are more or less subordinate to human interests and this is most obvi-ous regarding farm animals A health definition that puts priority to the physical and psychological well-being of an animal is misleading in relation to the general purpose of livestock production
In their veterinary dictionary, Blood and Studdert [14,15] express similar thoughts as Martin and co-workers [1], as they claim that health is "a state of physical and psycho-logical well-being and of productivity including reproduc-tion" Although this definition is very short, it mixes two different approaches to health, which could be regarded
as contradictory At first there may not be any conflict between well-being and productivity, but how do we make priority between these two aspects if they are in con-flict Are both parts necessary to fulfil in order to be healthy? This dual health definition leads us to the last category of health definitions, which includes productiv-ity aspects
5 Health as productivity including reproduction
The previous definitions could be seen as universal, i.e the health definitions could be applied to all animals including humans However, it would probably be hard
to use a health definition that equalises health to produc-tivity, as a general health definition for humans or other non-producing animals, e.g pets
The idea that health in animals solely is the same as pro-ductivity is quite uncommon in the literature, although it
is e.g proposed by C S G Grunsell in Black's veterinary dictionary [31], where it is stated that health "is now more accurately regarded as a state of maximum economic pro-duction"
Trang 5Even if it is rare to define health purely in productivity
terms, several authors incorporate elements of
reproduc-tion and productivity in their definireproduc-tion of health for farm
animals For example, Aspinall [32] states that "a healthy
animal grows, reproduces, and behaves in a manner
which has come to be regarded as normal for its species
and type"
In the book "Veterinary medicine: A textbook of the
dis-eases of cattle, sheep, pigs, goats & horses" [available in
several editions e.g [7]], it is proposed that disease
tradi-tionally has been defined as "abnormality of structure or
function" and that it has long been widened to embrace
subclinical diseases Furthermore, it is reported that the
concept of disease also includes "failure to produce" at
expected level of nutritional supply and environmental
quality But the authors also declare that "the detection of
residues of disqualifying chemical in foods of animal
ori-gin will also come to be included within the scope of
dis-ease" This extended definition of health is not just
relevant to the individual animal but also cover the
envi-ronmental effects
David Sainsbury [33] proposes a slightly modified health
definition related to productivity He introduces the term
"positive health", which he defines as" the provision of a
complete diet, an environment that is optimal for the
ani-mal's physiological needs, comfortable to the aniani-mal's
senses, in which the animal is secure and free from fear,
and with no undue challenge by pathogenic
micro-organ-isms or predators" Sainsbury's definition is interesting as
it is not just a describing health, but the definition is also
normative, i.e telling us how health should be He claims
that "good health is the birthright of every animal that we
rear, whether intensively or otherwise" He is also
extend-ing health beyond the subjective health state of the
ani-mal, as he argues that medication to control disease is not
giving true health to the animal although the animal
appears to be healthy
General discussion
It was rare that veterinary textbooks gave explicit
defini-tions of health and disease The main reason for that may
be that the general purpose of the textbooks was not to
investigate what is healthy or what is diseased in principle,
but to describe diseases and their causes and
conse-quences
It was common that textbooks use different aspects of
health definition [20] This makes it harder to actually
know what the main health idea is in a textbook When an
explicit definition of health was presented in a textbook it
was almost always given without references to other
health definitions It can be assumed that the reason for
this is that the authors were focused on the general topic
of the book and not philosophy of health
The general debate of welfare in animals was never referred in veterinary textbooks within this study, and the authors seemed to write in isolation from other authors' definition of health and disease However, there were exceptions from this in the books of veterinary homeopa-thy All three books about veterinary homeopathy found were referring to what the authors found as incorrect health definitions, i.e the mechanistic approach they attributed the school of classic veterinary medicine [11-13]
Homeopathic health definitions were stated to be 'holis-tic' and were mainly based on the idea that health is depending on homeostasis However, as health definition
of conventional veterinary textbooks also could be based
on the homeostasis idea, it can not be concluded that 'homeostasis thinking' logically leads to homeopathic medicine, as mention above This observation may illus-trate that the basic theory behind a health definition do not have inevitable consequences for the veterinary prac-tice It seems like the explicit definition of health stated by
an author had little or no impact on how health and dis-ease were handled within the profession
Veterinary medicine would probably gain on a more intense discussion about the concept of health A veteri-narian that never contemplates the health concept would merely be an "animal mechanic", who just needs to find out in what way the animal is broken, and then fix it according to the manual If the concepts of health and dis-ease were more clearly defined, the communication of e.g zoonotic hazards to the public would become more robust Furthermore, the general discussion of animal welfare issues would become more relevant if the basic concepts of health and disease were more commonly pen-etrated in the debate
Conclusion
The concepts of health and disease are rarely given explicit definitions in veterinary textbooks The definitions found could be split into five categorised of health definitions There was no obvious connection between stated health definition and medical approach, i.e classic veterinary medicine or alternative veterinary medicine Veterinary medicine would gain from a broader theoretical discus-sion about health and disease
Competing interests
The author(s) declare that they have no competing inter-est
Trang 6Publish with Bio Med Central and every scientist can read your work free of charge
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Acknowledgements
This work was conducted as a part of the project "Health and welfare in
the world of animals and humans" in collaboration with Bo Algers at SLU
Skara, Lennart Nordenfelt, Henrik Lerner and Anders Nordgren at the
Uni-versity of Linköping, and Ingemar Lindahl at the UniUni-versity of Stockholm
The project was funded by the Swedish Council for Working Life and Social
Research (FAS), grant no 2001-2317.
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